The present invention relates to a suspension damper and more particularly, to a strut-type suspension damper with a hydraulic stop for use in vehicular applications.
A suspension strut is a type of damper that operates in vehicular suspensions as both a damping device and as part of the suspension's load bearing structure. Hydraulic struts are conventionally known wherein a piston with a connected piston rod is slidably carried in a fluid-filled tube. A rod guide at the top end of the tube slidably engages the piston rod. It is also known to provide a mechanical rebound stop which is fixedly engaged to the piston rod and is contactable with the rod guide to provide a means of limiting the maximum extension of the piston rod from the damper.
A typical rebound stop is generally equipped with a resilient bumper made of material such as rubber or urethane. The bumper is designed to cushion the engagement of the rebound stop with the rod guide at the end of strut travel in the rebound direction. This type of a mechanical stop tends to result in somewhat of an abrupt means of limiting travel during rebound.
It is also known to provide a hydraulic rebound stop with a shock-absorber type of damper. Such a device is disclosed in U.S. Pat. No. 3,621,949. These hydraulic rebound stop devices have generally been limited in application to shock-absorber type dampers for a variety of reasons. One factor that has been a hindrance in applying hydraulic rebound stops to strut-type dampers is that the rod guide bearing in a strut is of a more complicated design than that found in a shock absorber. The strut type of rod guide is not amenable to application of the hydraulic rebound stop as typically used with shock-absorber type dampers.
A second complicating factor involves the nature and the performance of a strut. The generally steeply increasing nature of the pressure rise in a typical hydraulic stop as used in shock-absorber type dampers is acceptable when applied to a shock absorber but would generally be considered undesirable in the performance of a strut-type damper.
A third complicating factor is related to the nature of a strut-type damper as compared to a shock absorber. A shock absorber generally only provides damping in the longitudinal direction between the sprung and unsprung masses of a vehicle. In contrast, in addition to providing the damping function in a suspension system, a strut-type damper must support lateral loading in the suspension system and must be adaptable to providing a turning function when used on the front suspension of a vehicle. Therefore, in light of differences between strut-type dampers and shock-absorber type dampers, hydraulic rebound stops have generally been limited in application to the shock-absorber type.